In the “Star Trek” universe, most of the good real estate is on “Class M” planets — worlds like Earth, which can support human life. Present-day scientists don’t use that classification — not yet, anyway. But they do classify some asteroids as type M. And NASA is about to send a spacecraft to study the largest of them. Psyche — named for the Greek goddess of the soul — is in the asteroid belt, between the orbits of Mars and Jupiter. It’s shaped a bit like a potato, with an average diameter of about 140 miles. An asteroid is a member of type M if it has a high concentration of metals — especially iron and nickel. And that’s true of Psyche. Originally, scientists said it might be almost completely metal. They even estimated the value of that metal at around 10 billion billion dollars. More-recent observations say the proportion of metals could be around half, with much of the asteroid consisting of empty space. Psyche might once have been part of a small planet. Its gravity was strong en
